A paramedic was being questioned by police today on suspicion of murdering his ex-girlfriend in a hospital car park.
Nurse Jane Clough, and the suspect, named locally as Jonathan Vass, had lived and worked together before the fatal stabbing last night.
Miss Clough, 26, had just finished her shift in the Accident and Emergency unit at Blackpool Victoria Hospital and was walking to her car when she was stabbed by an attacker who then left the scene on a bicycle.
Police were called to the scene in the staff car park at about 8.30pm last night and the nurse was rushed to the A&E unit where she worked, just 100 yards away.
Her colleagues battled to save her but she was pronounced dead shortly afterwards.
Vass, 30, was arrested at about 7.30am today in his ex-partner's village of Barrowford, near Nelson, Lancashire.
He is understood to have worked alongside Miss Clough at the hospital until he was recently transferred elsewhere within the health trust.
A Lancashire Police spokesman said: "A post-mortem examination to establish the cause of death is due to take place later today.
"A 30-year-old man from Preston was arrested on suspicion of murder in Barrowford this morning and is currently in police custody."
Detective Chief Inspector Neil Esseen, who is leading the investigation, said: "This is a tragic incident and our thoughts are with Jane Clough's family, who are being supported by specially trained officers.
"There is a dedicated team of detectives working on this case and we are following up a number of lines of inquiry. However, I would like to appeal to anybody who has information they think may help with this investigation to contact police."
A bunch of flowers was left outside Miss Clough's end-terrace home in Camden Street, Barrowford, today.
A neighbour said the nurse had just returned to work after having a daughter and the couple had previously lived together for about 18 months.
He said: "I saw a few police cars driving around the street here this morning but I didn't see him (Vass)."
Miss Clough's parents, who also live in Barrowford, said they were too upset to talk about the incident.
Marie Thompson, director of nursing and quality at Blackpool, Fylde and Wyre Hospitals NHS Foundation Trust, said: "We are all shocked and devastated by the news of the tragic death of A&E nurse Jane Clough.
"We would like to offer our sincerest condolences to Jane's family, friends and work colleagues at this difficult time.
"Jane had worked as a registered nurse in the A&E Department at Blackpool Victoria Hospital for four years and was a valued and popular member of the team.
"She was described by her work colleagues as a very caring, compassionate and highly competent A&E nurse.
"Staff from across the Trust are extremely distressed and shocked by what has happened and we are currently offering them support and counselling."
Hospital porter Vaughan Cochrane, 54, of Whinney Heys Road - opposite the car park - said: "She was always smiling, a really nice girl.
"From what I can gather, she had just finished her shift and then something tragic happened. I've spoken to a few people at the hospital about it but no-one knows the full details yet.
"Me and my wife were on our way back from a meal when we got a phone call to say there was lots of police activity outside our house.
"When were got home there were police cars everywhere and a helicopter overhead."
A police officer stood guard at the entrance to the staff car park in Whinpark Avenue today.
One bouquet of flowers had been placed there, bearing a message which read: "Such a waste of a life RIP."
Two white forensic tents were erected in the car park - one covering two vehicles, including a black Vauxhall Corsa, and the other directly in front.
The car park, situated near a suburban area, was cordoned off.
Anyone with information on the stabbing should call police on 0845 125 3545 or Crimestoppers, anonymously, on 0800 555111.